Files and other ultrasonic instruments are used to remove the tooth pulp as well as to clean, shape and disinfect inside the root canals during endodontic treatments. Importantly root canals are very small in length as well as in caliber. Thus, a high degree of tactile perception and control is required during the endodontic treatment. As part of the procedure, the operator first obtains an image of the inside of the problem tooth. This shows whether the root canal is straight or crooked, is unobstructed or obliterated, has side channels or is calcified. The image can also be used to approximate the depth of the root canal. For an exact depth, the apex locator utilizing electrical resistance of tooth tissues is used. A working distance indicator, or “stop,” is attached to the file or other instrument to mark the apex distance and operatory limit.
There are in the market ultrasonic systems with hand pieces onto which ultrasonic instruments are fastened. In many circumstances, these ultrasonic instruments have replaced the inexpensive endodontic files used without benefit of ultrasound. These ultrasonic instruments are fastened to the ultrasonic hand piece in a similar way to how a drill bit is fitted to an electric drill.
The current ultrasonic system has two drawbacks: First, it delays the procedure while the operator unfastens one instrument and fastens another to the hand piece. Second, the operator experiences poorer tactile perception and control of the instrument, as compared to operating light-weight files by hand.
The above described ultrasonic systems have been shown to create accidental perforations, ledges, “transport of the apical region,” files fractures, over enlargement of the canals and other procedural errors. Despite their advantages, these factors have caused experts to stop recommending ultrasound use for the canal preparation. Currently, these ultrasonic systems are mostly used to help in the disinfection process of the treatment. The operator removes tissue and shapes the canal manually or mechanically with files (without ultrasound) and frequently switches to ultrasonic disinfection with fluid and then back to the other process.